Hydraulic pumps and motors

ABSTRACT

An hydraulic machine comprising a body, a member rotatably mounted in the body about a fixed axis, a plurality of pistons connected to the member by respective universal joints, a rotor having a plurality of bores within which the pistons are slidably engaged, the opposite end of the rotor from which the pistons enter being in facial contact with a ported surface on a part which is angularly movable in the body, about an axis which is inclined to the axis of the member, and is also inclined with respect to a plane which is perpendicular to said surface, angular movement of the part varying the strokes of the pistons, and the center of the surface coinciding with the axis of the rotation of the rotor, and being offset from the axis about which the part is angularly movable.

United States Patent [72] Inventor [22] Filed Apr. 15, 1969 [45] Patented Dec. 28, 1971 [73] Assignee Joseph Lucas (Industries) Limited Birmingham, England [54] HYDRAULIC PUMPS AND MOTORS 4 Claims, 12 Drawing Figs.

[52] U.S. Cl 60/53, 91/506 51 lnt.Cl ..F16d 31/02, F0112 13/04 [50] Field of Search 60/53; 103/162, 162 V, 162 0; 91/198-202, 484, 485; 92/57 [56] References Cited UNITED STATES PATENTS 2,604,856 7/1952 Henrichsen 60/53 2,975,597 3/1961 Arz 60/53 3,040,532 6/1962 Thoma et a1 60/53 2,847,938 8/1958 Gondek 103/162 3,156,192 11/1964 Austin et a1 103/162 3,204,411 9/1965 Stockton 60/53 FOREIGN PATENTS 1,063,461 8/1959 Germany 91/504 Primary Examiner-William Li Freeh Anorney- Holman 84 Stern ABSTRACT: An hydraulic machine comprising a body, a member rotatably mounted in the body about a fixed axis, a plurality of pistons connected to the member by respective universal joints, a rotor having a plurality of bores within which the pistons are slidably engaged, the opposite end of the rotor from which the pistons enter being in facial contact with a ported surface on a part which is angularly movable in the body, about an axis which is inclined to the axis of the member, and is also inclined with respect to a plane which is perpendicular to said surface, angular movement of the part varying the strokes of the pistons, and the center of the surface coinciding with the axis of the rotation of the rotor, and being offset from the axis about which the part is angularly movable.

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SHEET 2 [IF 4 INVENTOR [9J1 ZIP ATTORNEYS PATENTED M82819?! SHEET t 0F 4 INVENTOR I? .I IFI'E'LO BYM ATTORNEYS HYDRAULIC PUMPS AND MOTORS This invention relates to hydraulic variable stroke, reciprocating piston-type machines, which can be used as pumps or motors, of the kind comprising a body, a member rotatably mounted about a fixed axis within rotate. body, a plurality of pistons connected to the member by respective universal joints, a rotor having a plurality of bores which are occupied by the pistons respectively, the rotor being rotatable with the member, the opposite end of the rotor from which the pistons enter being in facial contact with a ported surface on a part, said part being movable to vary the inclination of said surface and the rotor with respect to the axis of rotation of the member, thereby to vary the strokes of the pistons in the bores in the rotor, as the member and rotor rotate. Such a machine will, for convenience, be referred to as being of the kind specified.

The object of the invention is to provide a machine of the kind specified in a form in which the adjustment of the strokes of the pistons can be readily accomplished.

In accordance with the present invention, an hydraulic machine of the kind specified is characterized in that the ported part has said surface, and is movable angularly in the body about a fixed axis which is inclined both to the axis of rotation of the member and also to a plane which is perpendicular to said surface, such angular movement varying the strokes of the pistons, and the center of the surface which coincides with the axis of rotation of the rotor, is offset from the axis about which the part is angularly movable.

A further object of the invention is to provide an hydraulic transmission system in a convenient form.

In accordance with a further aspect of the invention there is provided an hydraulic transmission system comprising an hydraulic pump of the kind set forth in the preceding paragraph arranged to be driven by a prime mover, an hydraulic motor of the kind set forth in the preceding paragraph to which the pump supplies motive fluid, the respective bodies being secured together and the surfaces against which the respective rotors engage being provided upon opposite sides of a single part, said part being mounted for angular movement about a fixed axis which is inclined to the axes of rotation of the pump and motor members and also to respective planes which are perpendicular to said surfaces, such angular movement varying the strokes of the pump and motor respectively, and the centers of the surfaces which coincide with the respective axes of the rotors, are offset from the axis about which the part is movable.

The invention will now be described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a diagrammatic representation of a pump constructed in accordance with this invention,

FIG. 2 is a side elevation view of an angularly movable part of the pump in a position corresponding to maximum piston stroke,

FIG. 3 is a front view in the direction of the arrow 3 in FIG.

FIG. 4 is a similar view to FIG. 2, but showing a position corresponding to half maximum piston stroke,

FIG. 5 is a front view in the direction of the arrow 5 in FIG. 7

FIG. 6 is a similar view to FIG. 2, but showing a position corresponding to zero stroke,

FIG. 7 is a front view in the direction of arrow 7 in FIG. 6,

FIG. 8 is a diagrammatic representation of a transmission mechanism having a pump and a motor both constructed in accordance with the invention,

FIG. 9 is a side elevation view of an angularly movable part of the mechanism in FIG. 8,

FIGS. 10 and 11 are views in the direction of arrows I0 and II in FIG. 9 respectively, and

FIG. 12 is an enlarged detailed cross-sectional view of the transmission mechanism illustrated in FIG. 8.

With reference to FIG. 1, there is illustrated an hydraulic pump of the kind specified and comprising a body 10 in which is mounted a driving member 11 supported for rotation about a fixed axis. The member 11 has connected to it, a driving shaft 12 extending outwardly of the body [0.

Connected to the member 11 by universal joints 13 are a plurality of pistons 14 disposed at angularly spaced positions about the fixed axis of the member I].

The pistons 14 engage in respective bores in a rotor 15 which is drivingly connected to the member 11 through the pistons 14, as well as through a universally jointed coupling indicated diagrammatically at 16.

The rotor 15 can be inclined with respect to the axis of rotation of the member II, and is illustrated in such a position, rotation of the member and rotor when the latter is in such a position resulting in reciprocation of the pistons 14 within the respective bores in the rotor 15.

The opposite end of the rotor 15 from the member 11 engages a surface 17 formed upon a part 18, there being a stub spindle 19 mounted upon said part I8, the axis of which passes through the center of said surface 17, and also coinciding with the axis of rotation of the rotor 15. This stub spindle 19 serves to support the rotor as it engages with said surface 17.

The part 18 is provided with ports which are shown in FIGS. 2 to 7. FIGS. 3, 5 and 7 show two kidney-shaped ports 18a and 18b opening onto the surface 17. These communicate respectively within the part 18, with elongated slots 18c, 1811 opening onto the cylindrical outer surface of the part 18. These slots 18c and 18d communicate, at all positions of the part 18 in the body, with an inlet and an outlet (not shown), in the body.

The part 18 is mounted in the body 10 for angular movement about an axis indicated at 20, and there is control means (not illustrated) for varying the angular position of the member 18 within the body 10. I

The axis 20 about which the part 18 is movable is inclined with respect to the axis of rotation of the member 11, and is also inclined with respect to a plane indicated at 21, with is perpendicular to the surface 17 formed on the part 18.

It will be observed that the plane 2I also contains the axis of rotation of the rotor 15 with respect to said surface 17.

In the example illustrated, the axis of rotation of the member 11 which is indicated at 23, and the axis 20 intersect at a point indicated at 22, and furthermore that plane 21 also passes through this point 22. The point 22 lies on a plane which also contains the axes of the universal joints 13 of all of the pistons 14.

Angular movement of the part 18 about the axis 20 causes the surface 17 to be moved orbitally with respect to said axis 20, and the position illustrated in FIGS. 1, 2 and 3 represents maximum possible stroke of the pistons 14.

The positions of the ports 18a and 18b in relation to the point at which the pistons are at maximum penetration into their bores in the rotor (indicated at Ma), are shown in FIG. 3 to be symmetrical about a plane passing through the point 14a and also containing all three axes 20, 21 and 23. This condition represents maximum displacement for the pump, when the pistons are travelling towards the ported surface 17, liquid in the bores will be delivered from the bores through the outlet port 18b to the body outlet and with inward travel liquid will be drawn in through the inlet port 18a. This will take place over the whole of the respective strokes of the pistons.

FIGS. 4 and 5 indicate the relative change in the positions of the ports 18a and 18b and the maximum piston travel point 140 after of angular movement of the part 18 about its own axis 20. It will be seen that the point 14a is only 45 from its original position (in FIG. 3).

The effect of this is that when the pistons are travelling towards the ported surface 17, delivery through the outlet port 18b will only occur over part of the travel of the pistons. During the remainder of such travel discharge will, instead, take place into the inlet port 18a. Inlet timing conditions will be similarly changed. The FIGS. 4 and 5 position of the part I8 will produce a change in stroke of the pistons, as distinct from the port timing change, such that the piston travel will be half the possible maximum.

FIGS. 6 and 7 show the relative positions of the ports 18a and 18b and the point 14a when 180 of angular movement has occurred. 180 of movement, however, positions the surface 17 perpendicular to the axis 23 of rotation of the member 11, the rotor axis also being coincident with that of the member 11. In this position no travel of the pistons will take place. It will be seen that the point Mr: has moved through 90.

This zero stroke position is thus equivalent to a timing change which renders any pumping action ineffective.

FIGS. 2 to 7 illustrate that any angular movement of the part 18 is accompanied by a port timing change which is effectively half the angle of movement of the part 18.

The change in the output or displacement of the pump is therefore effectively the difference produced by the timing change subtracted from the difference produced by the stroke change.

It is to be understood, moreover, that it is not essential that a true zero stroke position can be reached, and in the case of many pumps of this kind, it is desirable that the position of true zero stroke shall be unattainable.

Illustrated in FIG. 8, there is a transmission mechanism comprising an hydraulic pump and an hydraulic motor which embody the principle described with reference to the pump of FIGS. 1 to 7.

FIGS. 8 and 12 show the transmission mechanism which comprises a composite body or housing 24 within which is mounted a driving member 25 connected to a driving shaft 26 extending outwardly of the body 24.

Connected to the driving member 25 by respective universal joints 27 are a plurality of pistons 28. A rotor 29 has a plurality of angularly spaced parallel bores 30 in which the pistons 28 are slidably engaged, as seen in FIG. 3, and the member 25 and the rotor 29 are connected by a universally jointed coupling 31.

The opposite end of the rotor 29 from the member 25 engages a surface 32 formed upon a part 33 which is mounted upon bearings 34 within the body 24 of the mechanism.

Mounted in a bearing 35 in the center of the rotor 29 is a stub shaft 36 which extends into a bore in the part 33, a spring 37, acting between the outer race of the bearing 35 and a spring clip 38 engaging in a recess in the bore of the rotor which receives the shaft 36.

As illustrated, the axis of the shaft 36 and of the rotor 29 coincide with the axis of the universal joint of the coupling 31, whereby the latter is connected to the rotor 29.

The surface 32 on the part 33 is provided with respective kidney-shaped grooves 39, 40 with which the bores 30 of the rotor 29 communicate in turn.

At the opposite end of the composite body 24 of the mechanism there is provided an hydraulic motor having parts similar to those of the pump, and comprising a member 41 rotatably mounted in the body 24, the member 41 being connected to an output shaft 42, a plurality of universally jointed pistons 43 connected to the member 41, and being received in respective bores 44 in a rotor 45.

There is a stub shaft 46 carrying the rotor in a manner similar to the shaft 36 in the pump rotor 29.

The motor rotor 45 engages a surface 47 on the part 33, this surface having respective kidney-shaped grooves 48, 49 for communication with the bores 44 of the rotor 45 in turn.

The surfaces 32 and 47 are inclined with respect to the axis of the part 33, and are in similar relationship to the axes of rotation of the member 25 and 41 respectively, as is the surface 17 with respect to the axis of the member 11 of the pump illustrated in FIG. 1.

As shown in FIGS. 8, 9 and 10, however, the surfaces 32 and 47 are both offset with respect to the axis of movement of the part 33, and are, moreover, not parallel with one another. As illustrated, these surfaces are formed at opposite sides of the part 33, but the axes of the shafts 36 and 46 do not intersect. These axes are angularly spaced about the axis of movement of the part 33, as clearly illustrated.

The part 33 incorporates respective ducts (not illustrated) whereby the grooves 39 and 48 communicate with one another and whereby the grooves 40 and 49 communicate with one another, the pump being arranged to supply motive fluid to the motor during operation.

The hydraulic system within the mechanism is thus substantially a closed circuit, although it is necessary to provide a topup system (not shown) to ensure that the ducts in the part 33 are always filled with hydraulic fluid.

The part 33 also includes a drain passage 50 whereby controlled leakage of fluid from the bores of the rotors 29 and 45 through respective passages 51, 52 from the surfaces 32, 47 respectively can escape.

Angular movement of the part 33 is accomplished by means ofa rack 53 guided for movement in the body 24 adjacent to a toothed ring 54 formed integrally on the exterior surface of the part 33.

The transmission mechanism is so arranged that either the pump or the motor can achieve respective positions of maximum stroke, though these positions cannot be attained simultaneously.

When the pump is on zero stroke as illustrated in both FIGS. 8 and 12, the motor is on maximum stroke position. Angular movement of the part 33 causes the pump to be moved to increase the stroke towards a maximum which in this example is achieved after 75 of movement of the part 33 from the position illustrated.

During this movement of the pump, the motor stroke is reduced, the arrangement being such that the motor can never reach the zero stroke position at all.

The movement of the part 33 beyond a position of zero stroke for the pump will cause rotation of the motor in a reverse direction when required.

Angular movements of the part 33 also produce port timing changes in both pump and motor in similar manner to the changes described in relation to FIGS. 1 to 7.

The control mechanism is such that only a single external control is necessary for varying the ratio between the input shaft 26 and the output shaft 27 of the transmission mechanism, thus greatly simplifying the procedure for operation of a vehicle or other apparatus to which the mechanism is fitted.

The surfaces 32 to 47 are in this example, arranged at substantially equal angles with respect to the axis about which the part 33 moves, but such angles can be varied to suit the requirements for which the mechanism is intended.

Having thus described our invention which we claim as new and desire to secure by Letters Patent is:

1. An hydraulic transmission mechanism comprising a housing, a variable stroke hydraulic pump and a variable stroke hydraulic motor mounted in said housing; said pump and said motor each comprising a body, a member rotatably mounted about a fixed axis within said body, a plurality of pistons connected to said member by respective universal joints, a rotor having a plurality of bores in each of which bores one of said pistons is disposed, said rotor being rotatable with said member, the opposite end of said rotor from the end at which said pistons enter being in facial contact with a ported surface on a part, said part being movable to vary the inclination of said ported surface and of said rotor with respect to the fixed axis of rotation of said member, whereby the strokes of said pistons may be varied upon rotation of said member and said rotor; said respective bodies of said pump and said motor being secured together, and said ported surfaces comprising opposite faces of said part, said part being mounted for angular rotational movement about a fixed axis generally central thereof which is inclined to the axis of rotation of the pump and motor members and also to respective planes which are perpendicular to said ported surfaces, such angular movement varying the strokes of said pump and said motor respectively, the centers of said surfaces which coincide with the respective axes of said rotors being offset from the axis about which said part is movable, peripheral bearing between the periphery of which the centers of said ported surfaces are angularly spaced about the fixed axis of movement of said part.

4. A transmission mechanism as claimed in claim 1, in which said ported surfaces have respective kidney-shaped ports and said member has passages whereby pairs of such ports of said pump and motor communicate with one another.

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1. An hydraulic transmission mechanism comprising a housing, a variable stroke hydraulic pump and a variable stroke hydraulic motor mounted in said housing; said pump and said motor each comprising a body, a member rotatably mounted about a fixed axis within said body, a plurality of pistons connected to said member by respective universal joints, a rotor having a plurality of bores in each of which bores one of said pistons is disposed, said rotor being rotatable with said member, the opposite end of said rotor from the end at which said pistons enter being in facial contact with a ported surface on a part, said part being movable to vary the inclination of said ported surface and of said rotor with respect to the fixed axis of rotation of said member, whereby the strokes of said pistons may be varied upon rotation of said member and said rotor; said respective bodies of said pump and said motor being secured together, and said ported surfaces comprising opposite faces of said part, said part being mounted for angular rotational movement about a fixed axis generally central thereof which is inclined to the axis of rotation of the pump and motor members and also to respective planes which are perpendicular to said ported surfaces, such angular movement varying the strokes of said pump and said motor respectively, the centers of said surfaces which coincide with the respective axes of said rotors being offset from the axis about which said part is movable, peripheral bearing between the periphery of said part and said housing for permitting rotational movement of said part relative to said housing, and mechanical control means for effecting rotational movement of said part relative to said housing, said mechanical control means comprising cooperating rack and pinion means.
 2. A transmission mechanism as claimed in claim 1 in which the planes of said ported surfaces are inclined to one another.
 3. A transmission mechanism as claimed in claim 1, in which the centers of said ported surfaces are angularly spaced about the fixed axis of movement of said part.
 4. A transmission mechanism as claimed in claim 1, in which said ported surfaces have respective kidney-shaped ports and said member has passages whereby pairs of such ports of said pump and motor communicate with one another. 